The long-term objectives of this proposed research were: a) to utilize laboratory psychophysical techniques of vision tests with a view to developing more sensitive clinical measures of the natural history in the retinal vascular disease of diabetic retinopathy; b) where possible, to correlate the functional vision losses with observed retinal vascular changes; and c) to provide specific hypotheses and sensitive measurement techniques to be used for a follow-on randomized clinical trial involving the treatment and management of diabetic retinopathy. The original proposal called for the development of psychophysical vision tests during the first year, and to begin a pilot group of patients and normal controls. Instrumentation has been developed to measure the following functions: sensitivity of chromatic and luminance functions, spatial and temporal contrast sensitivity, low contrast acuity, glare recovery, Stiles-Crawford effect, hue discrimination and light adaptation properties of flicker resolution. Pilot studies on insulin dependent diabetics with background retinopathy showed significant slowing of the glare recovery function. Diabetic patients, whose vision is clinically normal, are shown to have substantial loss in blue cone mechanism sensitivity. The loss appears to be selective for chromatic processing in the visual pathways since the luminosity function appears to be completely in tact in these patients.